Prediction of Slamming Occurrence of Catamarans by idz16791

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									                 School of Applied Science




Prediction of Slamming Occurrence of Catamarans




                    Kristoffer Grande




     This thesis is presented as part of the requirements for
     the award of the Degree of Master of Science(Physics)
             of the Curtin University of Technology




                         August 2002
This thesis contains no material which has been accepted for the award of any
other degree or diploma in any university. To the best of my knowledge and
belief this thesis contains no material previously published by any other person
except where due acknowledgement has been made.




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                               ABSTRACT
       In this work the problem of slamming on the cross structure of
catamarans is studied. An introduction and overview of the problem is given.
Methods for predicting the slamming occurrence of high-speed power
catamarans and sailing catamarans are presented. Emphasis is placed on
developing methods that are practical to use in order to facilitate prediction of
slamming occurrence at the design stage. The methods used consist of three
steps: Ship motion prediction, slamming identification and slamming pressure
calculations. Existing linear and non-linear ship motion prediction theories are
used for high-speed power catamarans while a new strip theory has been
developed specifically for motion prediction of sailing multihulls. Predicted ship
motion results are compared to full-scale experiments, both for high-speed power
catamarans and sailing catamarans. A new direct method for identification of
slamming occurrence in the time domain is presented, as well as results using
probabilistic methods. A comparison between the two methods is presented.
Slamming pressure calculations are done using an existing two dimensional
slamming theory and are compared with analytical results. A parametric study is
done on two case study ships to investigate the effect of various hullform
parameters on the slamming occurrence. The methods and results presented are
of use to designers of high-speed power catamarans and sailing catamarans.




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                      ACKNOWLEDGEMENTS
       Writing this thesis would not have been possible without the many
persons that have helped me along the way. I would especially like to thank my
principal supervisor, Dr Jinzhu Xia, for his encouraging guidance and all the time
he has spent working together with me on this project. I would also like to thank
Dr Jørgen Krokstad who was my initial supervisor who organized the use of the
software packages VERES and SLAM 2D from Marintek, Norway. Thanks also
go to Emeritus Professor John Penrose, one of my co-supervisors who has been
very helpful and a source of inspiration with his humour. Dr Tony Armstrong of
Austal Ships has also been very helpful, and besides being a co-supervisor he has
provided me with a case study design from Austal ships. Dr Armstrong has also
been very helpful by sharing some of his practical experience from high-speed
catamarans and giving useful comments. I would also like to thank Dr Andrew
Tuite from Crowther Multihulls for providing a sailing catamaran case study
design and for useful input along the way. Thanks also go to Marintek, Norway
for providing the software packages VERES and SLAM 2D.


       All the staff at Centre for Marine Science and Technology have been very
friendly. A special thanks go to Mr Kim Klaka who initially suggested I should
travel from Norway to Western Australia to do this degree. Even though he has
not had any formal involvement in my work he has been extremely helpful all the
way. Mr Alec Duncan, Mr Amos Maggi and Mr Frank Thomas have all been a
great help with their knowledge about full-scale trials, data processing and
Matlab. Thanks also go to Mr Malcom Perry for his hard work with the
equipment for my full-scale trials. Thanks also go to Mr Ian Walker for kindly
letting me use his sailing catamaran Sally Malay for my full-scale trials. Finally a
big thanks go to Mr Philippe Peche for sharing of his vast practical experience
acquired through years of racing high performance catamarans around the world.




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               NOMENCLATURE
a       sectional added mass
A       added mass
b       sectional damping
B       damping
β       wave heading angle
βT      true wind angle
bwl     sectional waterline beam
c       sectional restoring coefficient
C       restoring coefficient
CG      boats centre of gravity
CM      midship coefficient
CP      prismatic coefficient
ε       slenderness parameter
η       displacement at CG
ηA      displacement amplitude
f       sectional Froude-Krylov force
F       exciting force
Fd      diffraction force
    f
F       froude-Krylov force
g       gravitational acceleration
h       sectional diffraction force
Hs      significant wave height
i       complex operator
k       wave number
LCB     longitudinal centre of buoyancy
LCF     longitudinal centre of flotation
LPP     length between perpendiculars
M       mass
ω       wave circular frequency
ωe      wave circular encounter-frequency
RAO     response amplitude operator


                            v
S       spectral ordinate
τ       waveform parameter
t       time
Tmean   wave spectra mean period
U       boat speed
V       wind speed
V1      wind speed parallel to x axis
V2      wind speed parallel to y axis
xc      sail strip chord length
ξ       relative displacement between the ship and wave surface
ζ       wave elevation
ζA      wave amplitude




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                                      TABLE OF CONTENTS

Abstract .......................................................................................................................iii
Acknowledgements ..................................................................................................... iv
Nomenclature ............................................................................................................... v
Table of Contents ....................................................................................................... vii
List of Tables .............................................................................................................. ix
List of Figures .............................................................................................................. x
CHAPTER 1: INTRODUCTION .............................................................................. 1
   1.1 Background ........................................................................................................ 1
   1.2 Statement of problem ......................................................................................... 5
   1.3 Historical review ................................................................................................ 6
   1.4 Present work..................................................................................................... 10
   1.4.1 Ship motion prediction.................................................................................. 11
       1.4.1.1 High-speed catamarans .......................................................................... 12
       1.4.1.2 Sailing catamarans ................................................................................. 12
   1.4.2 Slamming identification ................................................................................ 13
   1.4.3 Slamming pressure calculations.................................................................... 14
CHAPTER 2: SHIP MOTION PREDICTION ......................................................... 15
   2.1 Available methods............................................................................................ 15
   2.2 Present development ........................................................................................ 15
       2.2.1 Asymmetric strip theory............................................................................ 15
       2.2.2 Modelling of sail-forces ............................................................................ 23
       2.2.3 Implementation ......................................................................................... 26
   2.4 Work automation and visualisation.................................................................. 26
CHAPTER 3: SHIP MOTION PREDICTION RESULTS AND VALIDATION .. 28
   3.1 High-speed strip theory results......................................................................... 28
       3.1.1 Crowther 318............................................................................................. 28
       3.1.2 Crowther 318 modified ............................................................................. 31
       3.1.3 Austal Hull 63 ........................................................................................... 34
   3.2 Seakeeping validation ...................................................................................... 38
       3.2.1 Educat Full-scale Trials............................................................................. 38
       3.2.1 Austal Hull 63 full scale – simulation comparison ................................... 47

                                                               vii
     3.2.2 Marin model test ....................................................................................... 53
  3.3 Sailing multihull strip theory results ................................................................ 60
     3.3.1 Crowther Design 318 ................................................................................ 60
     3.3.2 Catamaran-Trimaran comparison.............................................................. 67
  3.4 Sailing multihull strip theory validation .......................................................... 72
     3.4.1 Sally Malay seakeeping trials.................................................................... 72
CHAPTER 4: SLAMMING IDENTIFICATION.................................................... 80
  4.1 Probabilistic method ........................................................................................ 80
  4.2 Direct method................................................................................................... 81
  4.3 Grouping of slamming events .......................................................................... 87
  4.4 Practical implementation.................................................................................. 87
Chapter 5: SLAMMING IDENTIFICATION RESULTS AND VALIDATION ... 89
  5.1 Austal Hull 63 .................................................................................................. 89
     5.1.1 Probabilistic method ................................................................................. 89
     5.1.2 Direct method............................................................................................ 93
     5.1.3 Comparison ............................................................................................... 98
  5.2 Crowther Design 318 ..................................................................................... 100
  5.2.1 Results from non-linear motion simulation................................................. 101
  5.2.2 Results from sailing multihull strip theory ................................................. 105
  5.3 Educat............................................................................................................. 109
CHAPTER 6: SLAMMING PRESSURE CALCULATIONS .............................. 112
  6.1 Calculation procedure .................................................................................... 112
  6.2 2-dimensional slamming theory..................................................................... 112
CHAPTER 7: SLAMMING PRESSURE RESULTS ........................................... 117
  7.1 Austal Hull 63 ................................................................................................ 117
     7.1.1 Calculated slamming pressures ............................................................... 118
     7.1.2 Slamming pressure distribution .............................................................. 121
  7.2 Crowther 318 original .................................................................................... 123
     7.2.1 Slamming pressure calculations.............................................................. 123
     7.2.2 Slamming pressure distribution .............................................................. 129
  7.3 Educat full-scale slamming measurements .................................................... 131
CHAPTER 8: PARAMETRIC STUDY ................................................................ 136
  8.1 Austal Hull 63 ................................................................................................ 136
  8.2 Crowther......................................................................................................... 138

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CHAPTER 9: CONCLUSIONS .............................................................................. 141
REFERENCES......................................................................................................... 143
Appendix 1: Background theory .............................................................................. 147
   STF Strip theory................................................................................................... 147
   High-speed strip theory ........................................................................................ 157
Appendix 2: Slamming pressure distributions ......................................................... 160
   Austal Hull 63 ...................................................................................................... 160
   Crowther 318 original .......................................................................................... 169
Appendix 3: Full-scale equipment ........................................................................... 183
       Data Acquisition system .................................................................................. 183
       Sensors ............................................................................................................. 183




                                           LIST OF TABLES
Table 3.1 Crowther 318 data...................................................................................... 28
Table 3.2 Austal Hull 63 data .................................................................................... 34
Table 3.3 Educat data................................................................................................. 39
Table 3.4 COFEA data............................................................................................... 54
Table 3.5 Catamaran/trimaran data ............................................................................ 68
Table 5.1 Full-scale slamming ................................................................................. 110
Table 7.1 kslam factor ................................................................................................ 120
Table 7.2 Pod kslam factor ......................................................................................... 126
Table 7.3 Main beam kslam factor ............................................................................. 128
Table 8.1 Austal Hull 63 variations ......................................................................... 136
Table 8.2 Slamming results 20 knots ....................................................................... 137
Table 8.3 Slamming results 30 knots ....................................................................... 137
Table 8.4 Slamming results 40 knots ....................................................................... 137
Table 8.5 Crowther design 318 variations ............................................................... 138
Table 8.6 Pod slamming results 5 knots................................................................... 138
Table 8.7 Main beam slamming results 5 knots....................................................... 139
Table 8.8 Pod slamming results 10 knots................................................................. 139
Table 8.9 Main beam slamming results 10 knots..................................................... 139
Table 8.10 Pod slamming results 15 knots............................................................... 139

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Table 8.11 Main beam slamming results 15 knots................................................... 140




                                         LIST OF FIGURES
Fig. 1.1 Typical fast ferry catamaran cross section...................................................... 1
Fig. 1.2 Typical cruising catamaran (30ft)................................................................... 2
Fig. 1.3 Typical ocean going racing catamaran (120ft) ............................................... 3
Fig. 1.4 110ft ocean racing catamaran ORANGE........................................................ 3
Fig. 3. 1 Crowther Design 318 ................................................................................... 28
Fig. 3. 2 Calculated Heave RAOs, Crowther 318 orig............................................... 30
Fig. 3. 3 Calculated Pitch RAOs, Crowther 318 orig................................................. 31
Fig. 3. 4 Calculated Heave RAOs, Crowther 318 mod.............................................. 32
Fig. 3. 5 Calculated Pitch RAOs, Crowther 318 mod................................................ 33
Fig. 3. 6 Austal Hull 63.............................................................................................. 34
Fig. 3. 7 Calculated Heave RAOs, Austal Hull 63..................................................... 35
Fig. 3. 8 Calculated Pitch RAOs, Austal Hull 63....................................................... 36
Fig. 3. 9 Heave Time series........................................................................................ 37
Fig. 3. 10 Pitch Time series........................................................................................ 38
Fig. 3. 12 Educat ........................................................................................................ 40
Fig. 3. 14 Trial Area................................................................................................... 42
Fig. 3. 15 Wave spectrum .......................................................................................... 44
Fig. 3. 16 Educat heave RAOs ................................................................................... 45
Fig. 3. 17 Educat pitch RAOs .................................................................................... 46
Fig. 3. 18 Full-scale heave RAOs, Austal Hull 63..................................................... 51
Fig. 3. 19 Full-scale pitch RAOs, Austal Hull 63 ...................................................... 52
Fig. 3. 20 Published COFEA body plan..................................................................... 55
Fig. 3. 21 Digitised COFEA body plan...................................................................... 55
Fig. 3. 22 Cofea heave RAOs..................................................................................... 56
Fig. 3. 23 Cofea pitch RAOs...................................................................................... 57
Fig. 3. 24 Cofea Waterlines ....................................................................................... 57
Fig. 3. 25 Cofea heave RAOs..................................................................................... 58
Fig. 3. 26 Cofea pitch RAOs...................................................................................... 59
Fig. 3. 27 Heave RAO without sail forces ................................................................. 61

                                                             x
Fig. 3. 28 Roll RAO without sail forces..................................................................... 62
Fig. 3. 29 Pitch RAO without sail forces ................................................................... 63
Fig. 3. 30 Heave RAO with sail forces ...................................................................... 64
Fig. 3. 31 Roll RAO with sail forces.......................................................................... 65
Fig. 3. 32 Pitch RAO with sail forces ........................................................................ 66
Fig. 3. 33 35m Catamaran (concept).......................................................................... 68
Fig. 3. 34 35m trimaran (concept).............................................................................. 69
Fig. 3.35 35m Catamaran lines plan .......................................................................... 69
Fig. 3.36 35m Trimaran lines plan ............................................................................. 69
Fig. 3. 37 Heave RAO comparison 15 knots ............................................................. 70
Fig. 3. 38 Heave RAO comparison 25 knots ............................................................. 70
Fig. 3. 39 Pitch RAO comparison 15 knots ............................................................... 71
Fig. 3. 40 Pitch RAO comparison 25 knots ............................................................... 71
Fig. 3. 41 Sally Malay ................................................................................................ 73
Fig. 3. 42 Trial Area................................................................................................... 74
Fig. 3. 43 Typical port tack upwind trial run ............................................................. 75
Fig. 3. 44 Heave and Wave spectra............................................................................ 76
Fig. 3. 45 Pitch and wave slope spectra ..................................................................... 77
Fig. 3. 46 Full-scale heave RAOs .............................................................................. 78
Fig. 3. 47 Full-scale pitch RAOs................................................................................ 79
Fig. 4.1 Local origin................................................................................................... 82
Fig. 4.2 Displacements............................................................................................... 82
Fig. 4.3 Wave elevation at arbitrary location............................................................. 85
Fig. 5.1 Austal Hull 63 slamming location ................................................................ 89
Fig. 5.2 Predicted slamming occurrence .................................................................... 91
Fig. 5.3 Predicted slamming occurrence .................................................................... 91
Fig. 5.4 Predicted slamming occurrence .................................................................... 91
Fig. 5.5 Predicted slamming occurrence .................................................................... 92
Fig. 5.6 Predicted slamming occurrence .................................................................... 92
Fig. 5.7 Predicted slamming occurrence .................................................................... 92
Fig. 5.8 Predicted slamming occurrence .................................................................... 93
Fig. 5.9 Predicted slamming occurrence .................................................................... 94
Fig. 5.10 Predicted slamming occurrence .................................................................. 94
Fig. 5.11 Predicted slamming occurrence .................................................................. 94

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Fig. 5.12 Predicted slamming occurrence .................................................................. 95
Fig. 5.13 Predicted slamming occurrence .................................................................. 95
Fig. 5.14 Average impact velocity ............................................................................. 96
Fig. 5.15 Average impact velocity ............................................................................. 96
Fig. 5.16 Average impact velocity ............................................................................. 96
Fig. 5.17 Average impact velocity ............................................................................. 97
Fig. 5.18 Average impact velocity ............................................................................. 97
Fig. 5.19 Average impact velocity ............................................................................. 97
Fig. 5.20 Predicted slamming occurrence .................................................................. 98
Fig. 5.21 Predicted slamming occurrence .................................................................. 99
Fig. 5.22 Predicted slamming occurrence .................................................................. 99
Fig. 5.23 Predicted slamming occurrence .................................................................. 99
Fig. 5.24 Predicted slamming occurrence ................................................................ 100
Fig. 5.25 Predicted slamming occurrence ................................................................ 100
Fig. 5.26 Crowther design 318 slamming locations................................................. 101
Fig. 5.27 Predicted slamming occurrence ................................................................ 102
Fig. 5.28 Predicted slamming occurrence ................................................................ 102
Fig. 5.29 Predicted slamming occurrence ................................................................ 102
Fig. 5.30 Predicted slamming occurrence ................................................................ 103
Fig. 5.31 Average impact velocity ........................................................................... 103
Fig. 5.32 Average impact velocity ........................................................................... 104
Fig. 5.33 Average impact velocity ........................................................................... 104
Fig. 5.34 Average impact velocity ........................................................................... 104
Fig. 5.35 Predicted slamming occurrence ................................................................ 106
Fig. 5.36 Predicted slamming occurrence ................................................................ 106
Fig. 5.37 Predicted slamming occurrence ................................................................ 106
Fig. 5.38 Predicted slamming occurrence ................................................................ 107
Fig. 5.39 Average impact velocity ........................................................................... 107
Fig. 5.40 Average impact velocity ........................................................................... 108
Fig. 5.41 Average impact velocity ........................................................................... 108
Fig. 5.42 Average impact velocity ........................................................................... 108
Fig. 5.43 Slamming sensor mounted on Educat....................................................... 109
Fig. 5.44 Simulated relative motions and slamming for slamsensor ....................... 110
Fig. 5.45 Simulated relative motions and slamming for sidehulls........................... 111

                                                       xii
Fig. 6.1 Local origin................................................................................................. 113
Fig. 6.2 Fluid domain ............................................................................................... 114
Fig. 7.1 Slamming pressure panel Austal hull 63 .................................................... 117
Fig. 7.2 Wetdeck section.......................................................................................... 118
Fig. 7.3 Impact pressure time history....................................................................... 119
Fig. 7.4 Average impact pressure time history ........................................................ 120
Fig. 7.5 Slamming pressure distribution .................................................................. 121
Fig. 7.6 Slamming pressure distribution .................................................................. 121
Fig. 7.7 Slamming pressure distribution .................................................................. 121
Fig. 7.8 Slamming pressure distribution .................................................................. 121
Fig. 7.9 Slamming pressure distribution .................................................................. 122
Fig. 7.10 Slamming pressure distribution ................................................................ 122
Fig. 7.11 Pod section................................................................................................ 123
Fig. 7.12 Impact pressure time history..................................................................... 124
Fig. 7.13 Average impact pressure time history ...................................................... 125
Fig. 7.14 Main beam section .................................................................................... 126
Fig. 7.15 Impact pressure time history..................................................................... 127
Fig. 7.16 Average impact pressure time history ...................................................... 128
Fig. 7.17 Pod slamming pressure distribution.......................................................... 129
Fig. 7.18 Pod slamming pressure distribution.......................................................... 129
Fig. 7.19 Pod slamming pressure distribution.......................................................... 129
Fig. 7.20 Pod slamming pressure distribution.......................................................... 129
Fig. 7.21 Main beam slamming pressure distribution.............................................. 130
Fig. 7.22 Main beam slamming pressure distribution.............................................. 130
Fig. 7.23 Main beam slamming pressure distribution.............................................. 130
Fig. 7.24 Main beam slamming pressure distribution.............................................. 130
Fig. 7.25 Pod slamming pressure distribution.......................................................... 131
Fig. 7.26 Pod slamming pressure distribution.......................................................... 131
Fig. 7.27 Pod slamming pressure distribution.......................................................... 131
Fig. 7.28 Pod slamming pressure distribution.......................................................... 131
Fig. 7.29 Main beam slamming pressure distribution.............................................. 131
Fig. 7.30 Main beam slamming pressure distribution.............................................. 131
Fig. 7.31 Typical impact pressure ............................................................................ 132
Fig. 7.32 Calculated slamming pressure, 1 m/s impact ........................................... 133

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Fig. 7.33 Pressure distribution for 2D section ......................................................... 134




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